There was a stuttering issue for me before where my character would slip and slide (not lag-based) and that was eventually fixed. 0 problems with that for a while, and enjoying the beta client quite a bit now.
However, I experience these issues when I use a horse (in the regular client, too):
1. When bumping someone or after colliding with another horse (without the rearing animation), my horse begins to skip frames along my intended path. On my screen, it looks like I am constantly teleporting and I have little control over the horse for this period of time. I need to come to a stop for a few seconds to fix this issue.
2. When I get dehorsed, sometimes I may slide far out of reach of where I was supposed to land.
3. The horse soaks an attack at a location separate of where it is located onscreen.
I was wondering if it would be possible to fix 1 or 2 at least. With bad luck, 1 seemed to happen on almost 1/4 of my bumps. 3 seems like an overarching issue with hitboxes in general, but I just thought it was worth pointing out.